1. Field of the Invention
The present invention relates to a film strip cartridge having a film lock designed to arrest longitudinal movement of the film by causing a lock means to penetrate one of the perforations along the margin of the film.
2. Description of the Prior Art
Conventional strip film cartridges have a guide channel thru which film may be advanced in a first direction for engagement with a complimentary film strip projector or in a second direction for film rewind. During the normal handling of these cartridges, it is possible for the film to be inadvertantly pulled from the cartridge. The film must then be manually coiled and the cartridge reloaded. Film locks have been developed to prevent movement of the film in the cartridge. One such type of film lock is described in U.S. Pat. No. 3,692,392 filed Sept. 19, 1972. The lock described therein utilizes a rigid pin in combination with an endless film cartridge to provide a means to retain the film in proper relationship with the projecting aperture. The pin penetrates one of the margin perforations of the film to prevent longitudinal movement of the film. Such pin locks are generally satisfactory. However, if the locked film is inadvertantly pulled with excessive force, the rigid pin can tear thru the portion of the film separating the aperture.
The present invention provides a film lock for penetrating a marginal perforation to lock the film against inadvertent longitudinal movement. In an alternate embodiment, the locked film may be pulled with excessive force to cause the locking means to extract itself from the perforation without causing damage to the film.